Fracking, the controversial shale gas extraction technique, has been given the green light to resume in the UK.

Moves by gas company Cuadrilla to exploit the unconventional gas in Lancashire were put on hold 18 months ago after fracking, which uses high-pressure liquid to split rock and extract gas, caused two small earthquakes.

Energy Secretary Ed Davey said on Thursday that fracking could resume in the UK, subject to new controls which aim to reduce the risk of seismic activity.

Fracking has many opponents concernend about its environmental impact

Davey said shale gas represented a promising new potential energy resource for the UK, although it was not yet known what contribution it could make to the energy mix, jobs and the economy.

He insisted that exploiting shale gas in this country would not undermine efforts to cut emissions to tackle climate change.

And he said that, as gas would be needed in coming decades for heating, cooking and electricity, there were advantages in developing domestic supplies.

The Treasury has already signalled its support for the budding industry, proposing tax relief for shale gas, and unveiling a gas generation strategy which potentially paves the way for a new "dash for gas".

But environmentalists warn that a continued reliance on gas would prevent the UK meeting targets to cut emissions and tackle climate change, and that shale has no place in the move to a low-carbon economy.

Concerns have also been raised, following widespread exploitation of shale resources in the US, that it can cause local environmental problems including polluting water supplies and damaging development.

Davey said: "Shale gas represents a promising new potential energy resource for the UK. It could contribute significantly to our energy security, reducing our reliance on imported gas, as we move to a low-carbon economy.

"We are still in the very early stages of shale gas exploration in the UK and it is likely to develop slowly.

"It is essential that its development should not come at the expense of local communities or the environment. Fracking must be safe and the public must be confident that it is safe.

"We are strengthening the stringent regime already in place with new controls around seismic risks. And, as the industry develops, we will remain vigilant to all emerging evidence to ensure fracking is safe and the local environment is protected."

The controls will include a traffic light system, requiring operators to stop if seismic activity reaches a certain level, magnitude 0.5, which is well below a quake that could be felt at the surface but higher than normal fracking levels.

Tessa Munt, Liberal Democrat MP for Wells, called for investment in renewable energy.

"The fracking debate is fundamental to the direction of UK energy policy," she said.

"Do we, as a country, want to scramble around trying to drag every last remnant of polluting fossil fuels from our earth before we understand fully the impact of this highly controversial technique?

"Or do we want to be serious about reducing our energy demand, improving the energy efficiency of our buildings, vehicles and equipment and embracing renewable energy, with its absolute energy security, declining costs, many new jobs and real growth?

"Even as a small part of the energy mix, a push for shale gas will swiftly descend into a commercial stampede and investment will leak away from the renewable sector.

"There is an alternative, it is better for our country, our beautiful county, our communities and our children.
"I know where I stand."